It’s early April 2015, and John Marzluff and I are standing with a film crew attempting to capture some footage of a crow funeral to compliment a story they are working on about Gabi Mann. I’ve already set the dead crow on the ground, it’s placed just out from a cherry tree resplendent in springtime blossoms. After only a few moments of waiting, the first crow arrives and alights on the tree, its head cocking around to get a better look at the lifeless black feathers beneath it. I hold my breath for the first alarm call, ready for the explosion of sound and the swarm of birds that will follow it. But it doesn’t come. Instead, the bird descends to the ground and approaches the dead body. My brow knits together in surprise but, ah well, I think, the shots of it getting so close and then alarm calling will make good footage. The audience will have no questions about what it is responding to. To my continued surprise, however, the silence persists; only now the crow has drooped its wings, erected its tail, and is approaching in full strut. No, no, this can’t be, I think. But then it happens. A quick hop, and the live crow mounts our dead one, thrashing in that unmistakable manner. “Is it giving it CPR?” someone asks earnestly. Still in disbelief, John and I exchange glances before shaking our heads and leaving the word “copulation” to hang awkwardly in the air. After a few seconds another bird arrives to the cherry tree and explodes in alarm calls, sending our first bird into its own fit of alarm, followed by a more typical mobbing scene. The details of what I’ve just witnessed as still washing over me when I hear John lean over to me…”You need to start your field season tomorrow.”

***

What crows do around dead crows is something I’ve dedicated much of my academic life to understanding. In the course of my first study, my findings made for a nice clear narrative: crows alarm call and gather around dead crows as a way of learning about dangerous places and new predators. Although there are other hypotheses we can’t rule out, certainly danger avoidance is at least partially driving this behavior. An important detail of that original study though, is that because of the way it was designed, with a dangerous entity always near the dead crow, our live crows were never in a position to ever get very close to our dead stimulus. So the possibility that they do other things around dead crows, like touching them, couldn’t be explored.

It’s been 3 years since that day in April and during that time it has taken every ounce of my power to remain tight lipped when journalists would ask “what’s the most interesting thing you’ve learned from your studies?” Because until we were able to scientifically vet the prevalence of this behavior, I wasn’t willing to say much about it for fear of making necrophilia mountains out of mole hills. But with our findings now officially available in the journal Philosophical TransactionsB, I am delighted to finally share what has been the most curious secret of my PhD: crows sometimes touch, attack, and even copulate with dead crows.

Although this statement is jarring in its own right, what really gives it power is that we know this not just from that first fateful day with the film crew, but through an experimental study testing the response of hundreds of birds over several years. That’s important because it allows us to say not just what they’re doing but possibly why they’re doing it (and at least why they’re not doing it). So how did we conduct this experiment?

First, I dove into the literature to try and see if there was any precedent for this kind of behavior in other animals. Although there have been no systematic studies, repeated observations of animals touching, harming, even copulating with their dead occur in dolphins, elephants, whales, and many kinds of primates, among some other animals. Based on this, we hypothesized that this behavior may arise from: attempts to eat it, attempts to learn from it, or a misuse of an adaptive response (like territoriality, care taking, mate guarding, etc.). To test these ideas I searched the neighborhoods of Seattle until I found a breeding adult pair and (while they weren’t looking) presented one of four stimulus options: An unfamiliar dead adult crow, an unfamiliar dead juvenile crow, a dead pigeon or a dead squirrel. The latter two stimuli being key in helping us determine if the behavior was food motivated, whereas the nature and prevalence of the interactions themselves (common, uncommon, exploratory, aggressive, sexual) helped us address the other hypotheses. In all, I tested 309 individual pairs of crows; or in other words, once again I freaked out a lot of Seattle residents wondering why there was a woman with a camera, binoculars, and some dead animals loitering in front of their house for long periods of time.

Our main findings are that crows touched the animals we would expect them to eat (pigeons and squirrels) more than the dead crows, and although crows sometimes make contact with dead crows, it’s not a characteristic way they respond. Because this behavior is risky, this seems to back up previous studies in crows that suggest that they are primarily interested in dead crows as a way of self preservation and avoiding danger.

A crow tentatively pokes at one of our dead crows

That said, in nearly a quarter of cases, crows did make some kind of contact with dead crows. Like with mammals, we saw that these behavior could be exploratory, aggressive and in rare cases even sexual (about 4% of crow presentations resulted in attempted copulations), with the latter two behaviors being biased towards the beginning of the breeding season. Importantly, the latter two categories of interactions were rarely expressed independently, and it was often a mixture of the first two; in rare cases, all three. In the most dramatic examples, a crow would approach the dead crow while alarm calling, copulate with it, be joined in the sexual frenzy by its presumed mate, and then rip it into absolute shreds. I must have gone through a dozen dead crows over the course of the study, with some specimens only lasting through a single trial. It was an issue that may have been insurmountable if not for the donations of dead crows by local rehab facilities and the hard work of my long time crow tech turned taxidermist, Joel Williams.

It’s hard to witness this behavior without wondering if maybe the crows somehow don’t recognize that it’s dead and are instead responding like they might to a living intruder or to a potential mate. So we tested that idea too, by conducting a second experiment where we presented either a dead crow or a life-like crow mount. The differences in their response was clear. They dive bombed the “live” crows and less often formed mobs, just like we would expect them to do for an intruder. They also attempted to mate with the “live” birds but in these cases it was never paired with alarm calling or aggression. So the issue doesn’t seem to be that they think it’s alive.

The fact that this behavior was rare, and often a mix of contradictory behaviors like aggression and sex, seems to suggest that none of those hypotheses I outlined earlier are a good fit for this behavior. Instead, what we think happens is that during the breeding season, some birds simply can’t mediate a stimulus (the dead crow) that triggers different behaviors, so instead they respond with all of them. This may be because the crow is less experienced, or more aggressive, or has some neurological issue with suppressing inappropriate responses. Only more experiments will help us determine what makes this minority of birds unique, and whether expressing these seemingly dangerous behaviors are the mark of the bird that is more, or less reproductively successful in the long haul.

So while there’s still much more left to be explore here, I can finally say that this is without a doubt some of the most interesting behavior in crows I’ve ever witnessed. I hope you will check out the publication here, and seek out all the other amazing work being reported in this special thanatology (death science) themed issue.

The dead crow being left is not a member of the murder or flock. As crows respond differently to a member of their group vs an outsider wouldn’t you expect members of the murder/flock to respond differently to a dead crow that is not a member of the flock than it would if it was a member?

I think it’s very possible. That said, we have done some anecdotal tests/observations were we were either in the right place right time to see a bird get killed or we found a banded dead crow on it’s territory and then removed it and put it back out. In both cases the responses weren’t different from they typical scold/mob response. But again, that’s just a few observations so I’ll say the jury is still out!

In Seward Ak we have a murder of crows with between 130 and 150 members per Christmas bird counts. I spent hundreds of hours each year with them from 2007 through 2014. I continue to visit them but not nearly as often or for as long during the years since. I have witnessed many funerals, but have never observed a dead crow being touched by another. Did you by chance control for familiarity of the dead crow?

Is it possible that this behavior varies from one geographic area to another or according to type of crow? I’ve read that there is some disagreement whether or not Northwestern crows are different from American crows, but think I recall your crows being Northwestern crows, too, which disproves that hypothesis!
Of course , most likely I was simply not present when the touching of dead crow occurred. Silly of me, but I hope not.

We did control for familiarity. These were all unfamiliar birds. Crows can certainly vary a lot behaviorally from region to the next even within the species, so I wouldn’t discount the possibility of regional differences (though for the record our crows are hybridized, mostly American crows). Were most of the deaths you witnessed biased towards one time of the year?

I would strongly suspect that there would be huge difference in responses to an unfamiliar crow, as to a crow that is actually a member of their group, a family member/spouse/offspring etc.

Humans can feel very much less about the death of a stranger than they will about the death of one of their own family or social group, so why wouldn’t another intelligent animal have a similar disconnect depending on if it’s a stranger or not?

Wow! And that last pic is NICE. I’ll bet that they didn’t know the dead individuals, dead in -their- neighborhoods, had something to do with the varied and surprising responses; it’s not something that normally happens. (The West Nile virus part of the story was unprecedented, too, but) I saw surviving friends and family stand quietly over dead indivs, juveniles vocalize agonizingly over dead parents, and mourning and grief in the weeks-months thereafter. Habitat Desaturation at Carolee Caffrey.com

Hm maybe they wouldn’t be acting so odd if a lady scientist hadn’t been sexually torturing them for YEARS. I am SO DONE with her terrible research. I hate to say these words, but this woman is a BIRD PERVERT. 🤢 SICK!

Couple questions. 1) why are you addressing me in the 3rd person? When you leave a comment on my blog you are essentially writing me a public email. Do you write all your emails this way? 2) I hate to discredit myself here, but I am only a scientist. It would take an additional FIVE YEARS of grad school to earn my Lady Science degree and, I’ll be honest, I’m just burnt out. 3) These were wild, free ranging birds under literally no obligation to do anything. In what way do perceive that I am “sexually torturing” them? Is being exposed to a dead body “sexual torture”? If so, I hope you are not pursing any kind of work in the mortuary sciences.

I hope you don’t feel peppered with questions, but I can’t help it. When I see something curious I pursue it. That’s how this whole this started, remember. I saw something I wasn’t expecting to see and then did three yeas of research in order to determine if it was a trend or not.

Ah yes, well now I don’t feel so bad about not seeing crow necrophilia. I did see several crows eating a (not dead) crow hit on the road. The poor struck bird was disemboweled, so no chance of veterinary care, so I euthanized it by cervical dislocation. This earned me my very first “marked for death” badge by the local crows, which lasted about 3 months thereafter. It was only 2 blocks from my house, so it was not super convenient, as the mobbing would happen soon after I left.

So they took you for a predator but it wore off after three months. That was fortunate. The crows mob red fox and all kinds of hawks that come through their territory (my backyard) relentlessly. In fact a beautiful hawk took down a crow, had it in its claws on the ground, and was mobbed by not only the crows that claim my yard but other crows (neighbors?). They swirled around it, attacked it from the ground and the air with claws, wings and beaks. There were so many surrounding it at first I couldn’t figure out what was going on because I couldn’t see the hawk with the crow. The crow was definitely alive. Eventually the crows relented and most of them flew into the trees surrounding the hawk. They did a lot of screeching. But the hawk won in the end. Seemed totally unfazed by the mob. It was a few days before the crows that claim my yard came back.

Hi Kaeli, Congratulations on your research and Doctorate.
As a lamb producer, I have heard it said before that one way to scare off crows (our Australian ravens) from being around lambing ewes and fresh lambs is to leave a dead crow in the field. Or more than one. Would that work, and why? Would we hang it, or leave it on the ground? And when placing it there, would we disguise ourselves and use a different vehicle? If I’m understanding the research, I would want crows to associate the danger to be with the place, or the stock, not with me.

Yes effigies can work as a deterrent for corvids, most effectively if paired with other negative stimuli like lights or noise, but obviously those latter two are not always as practical. Hanging them is probably a bit more effective because it will maximize exposure. More is more in this case, but I doubt you need more than three depending on how much area you’re trying to protect.

I would actually associate it with you and your work vehicles as much as possible. Their memories are not an either/or situation so they’ll learn the place regardless and then if they make the association with your car then that just further reinforces the scariness every time they see it out there. Hope that helps!

Hello, I stumbled upon your research on this matter purely by chance (I am a high school statistics student conducting an observational study of American crows). To be honest, I literally did a double-take at the title, like “wait… What!?” I read the article and was not disappointed. This is fascinating stuff! Just… corvids. I would never have guessed. Thank you for publishing this research!